An electric machine of said type may basically be designed as an electric motor or as a generator. It is in the present case preferably a generator which is used with an internal combustion engine, in particular in a motor vehicle, and which is normally referred to there as an alternator. The generator is particularly advantageously designed as a claw pole generator. In the case of a claw pole generator of said type, a front claw body and a rear claw body are mounted on a rotor shaft on both sides of a rotor winding, in such a way that the pole claws of the front claw body and pole claws of the rear claw body alternate in the circumferential direction and thus form electromagnetic poles which alternate with one another during the operation of the generator.
In the case of an electric machine of said type, the rotor has a rotor shaft which is led out through a front wall of the housing, wherein the rotor shaft has, at an outer side of the front wall, a drive element which serves for transmission of torque between the rotor and a drivetrain when the electric machine is incorporated into the drivetrain. In the case of the electric machine being used as a generator on an internal combustion engine, the generator is expediently incorporated into a belt drive of the internal combustion engine, such that the drive element is then a belt pulley which engages with a belt of the belt drive. Other configurations are basically also conceivable, however.
The electric machine may for example be incorporated into a chain drive. The drive element is then a gearwheel which then engages with a chain of the chain drive.
The rotor shaft is expediently rotatably mounted in a front bearing which is inserted into the front wall. Said front bearing, which is expediently a rolling body-type bearing, in particular a ball bearing, is subject to increased risk of contamination specifically if the electric machine is used in the region of an internal combustion engine, in particular in a motor vehicle. Contamination of the front bearing can however increase the friction in the front bearing, and intensify abrasion and thus also wear of the front bearing. In this case, it has been found that there is also a risk of contamination from an interior of the housing, in particular if a cooling air flow flows through the housing. A cooling air flow of said type may introduce contaminants from the surroundings of the electric machine into the interior of the housing. From there, the contaminants can pass between a rotor body of the rotor and an inner side of the front wall to the front bearing, and contaminate the latter. Such impurities comprise particles and liquids and suspensions and the like. Here, the contaminants may be composed of different materials. In the case of the electric machine being used in the region of an internal combustion engine, a high proportion of such contaminants is formed by fluids which are used in conjunction with the internal combustion engine and which pass into the surroundings as a result of leakages.
Whereas the front bearing can be protected relatively effectively by way of conventional seals at the outer side of the front wall, merely conventional seals generally cannot be used at the inner side owing to the hard operating conditions prevailing there.